Low-noise blower

ABSTRACT

A low-noise blower has an impeller with an impeller plate and a plurality of blades each attached to the impeller plate. Each blade has a tip and a leading surface with a first portion that is proximate to the tip and has a first radius that is within a range of 0.03-0.20 inch.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit of priority under 35 U.S.C.§120 as a continuation from U.S. patent application Ser. No. 13/931,465entitled “LOW-NOISE BLOWER,” filed on Jun. 28, 2013, the disclosure ofwhich is hereby incorporated by reference in its entirety for allpurposes.

BACKGROUND

Field

The present disclosure generally relates to gas compressors and, inparticular, to a centrifugal air blower.

Description of the Related Art

Patients with respiratory injury, such as chronic respiratory failure,may be provided with a respirator to assist with their breathing or, insevere cases, take over the breathing function entirely. Respiratorstypically provide a flow of air, or other breathing gases, at anelevated pressure during an inhalation interval, followed by anexhalation interval where the pressurized air is diverted so that theair within the patient's lungs can be naturally expelled. The inhalationinterval may be initiated upon detection of a patient's naturalinhalation or by the respirator

Respirators are available in a variety of sizes with different ranges ofair flows and pressures that can be provided. For example, a neonatalpatient will require a much lower pressure and volume of air per breaththan an adult, and many conventional respirators cannot provide accuratedelivery of pressurized air over this range of volumes and pressures.

In conventional respirators that use a blower to pressurize the gasprovided to the patient, the blowers that are used are loud and thenoise level in the patient's room is commonly 65 dB or more. This levelof noise may disrupt the patient's rest and sleep as well as causefatigue for the caregiver and may further obstruct diagnosis andmonitoring of the patient by masking the natural breathing noises thatprovide an indication of the patient's condition.

SUMMARY

It is advantageous to provide a small, quiet blower that can accuratelyprovide a flow of compressed gas over wide ranges of flow rate andpressure.

In certain embodiments, a blower is disclosed that has an impellercomprising an impeller plate and a plurality of blades each attached tothe impeller plate. Each blade has a tip and a leading surface thatcomprises a first portion proximate to the tip. The first portion has afirst radius that is within a range of 0.03-0.20 inch.

In certain embodiments, an impeller is disclosed that has an impellerplate having an outside edge with a first radius and a plurality ofblades attached to the impeller plate. Each of the plurality of bladescomprises a tip at the outside edge and a leading surface with a firstportion extending from the tip and a second portion that extends fromthe first portion with a second radius that is within the range of0.14-0.16 inch.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding and are incorporated in and constitute a part of thisspecification, illustrate disclosed embodiments and together with thedescription serve to explain the principles of the disclosedembodiments. In the drawings:

FIGS. 1-2 are top and bottom perspective views of an exemplary bloweraccording to certain aspects of the present disclosure.

FIG. 3 is an exploded view of the blower of FIG. 1 according to certainaspects of the present disclosure.

FIG. 4 is a perspective view of an exemplary impeller according tocertain aspects of the present disclosure.

FIG. 5 is a close-up plan view of a vane tip of the impeller of FIG. 3according to certain aspects of the present disclosure.

FIG. 6 is a perspective view of a conventional impeller.

FIG. 7 is a cross-section of the blower of FIG. 1 according to certainaspects of the present disclosure.

FIG. 8 is an enlarged view of a portion of FIG. 7 according to certainaspects of the present disclosure.

FIGS. 9A-9C are perspective views of the overmolded top housingaccording to certain aspects of the present disclosure.

DETAILED DESCRIPTION

It is advantageous to provide a relatively small, quiet blower that canaccurately provide a flow of compressed gas over wide ranges of flowrate and pressure.

In the following detailed description, numerous specific details are setforth to provide a full understanding of the present disclosure. It willbe apparent, however, to one ordinarily skilled in the art thatembodiments of the present disclosure may be practiced without some ofthe specific details. In other instances, well-known structures andtechniques have not been shown in detail so as not to obscure thedisclosure. In the referenced drawings, like numbered elements are thesame or essentially similar. Reference numbers may have letter suffixesappended to indicate separate instances of a common element while beingreferred to generically by the same number without a suffix letter.

While the discussion herein is directed to the provision of compressedair as part of a medical respirator, the disclosed concepts and methodsmay be applied to other fields that would also benefit from a quiet,portable source of compressed air. For example, conventional leafblowers that are commonly used to blow leaves and small garden debrisinto piles are quite loud and a blower of this type may be advantageousin place of the current blowers.

FIGS. 1-2 are top and bottom perspective views of an exemplary blower100 according to certain aspects of the present disclosure. In theconfiguration of FIG. 1, the blower 100 draws in ambient air, or othergases if connected to a source of gas, through inlet 119 of housing 112.Impeller 160 may rotate at a variable speed up to 30,000 rotations perminute (rpm), for example, to centrifugally accelerate the air andprovide a flow of pressurized air at outlet 118. In this embodiment, thehousing 112 comprises two parts, 112T and 112B (see FIG. 3) heldtogether with multiple clips 114. The section line A-A indicates thecross-sectional view of FIG. 7.

FIG. 2 is a perspective view of the blower 100 of FIG. 1 with the blower100 rotated so as to make the bottom housing portion 112B visible. Amotor 120 is attached to the housing 112 and the shaft of the motor (notvisible in FIG. 2) passes through the housing 112 and connects to theimpeller 160.

FIG. 3 is an exploded view of the blower 100 of FIG. 1 according tocertain aspects of the present disclosure. The top housing portion 112Thas an impeller cavity 119. The impeller 160 is at least partiallydisposed within the impeller cavity 119 when the blower 100 isassembled. The housing 112 comprises a collector 116 formed when the topand bottom housing portions 112T, 112B are mated. In this example, thecollector 116 is shaped as a volute having a circular cross-sectionalprofile along a radial plane of the housing 112, wherein the area of theprofile monotonically increases as the distance around the volute fromthe outlet 118 decreases. In certain embodiments, the volute may have anon-circular profile. In certain embodiments, the area of the profilemay be constant over a portion of the volute.

The top and bottom housing portions 112T, 112B also respectively includeedges 124U, 124L that are proximate to each other when the blower 100 isassembled and surround the impeller cavity so as to cooperatively definea slot(not visible in FIG. 3) that connects the impeller cavity 119 tothe collector 116. The lower housing portion 112B also includes a wall120 and a shelf 122 adjacent to the edge 124L. This region of the blower100 is described in greater detail with respect to FIG. 7.

FIG. 4 is a perspective view of a conventional impeller 10. Thisimpeller 10 has a plurality of vanes 12, 20 each having a leading edge14 and a trailing edge 16, although vanes 20 are shorter than vanes 12and are commonly referred to as “splitters.” Conventional vanes 12, 20have a three-dimensional curvature with a generally uniform thicknessfrom leading edge 14 to trailing edge 16, with some rounding of theoutside corners and filleting of the inside corners.

FIG. 5 is a perspective view of an exemplary impeller 160 according tocertain aspects of the present disclosure. The impeller 160 comprises animpeller plate 162 having a shaped surface 166 and a circular outsideedge 164 that are centered about an axis of rotation 161. In thisembodiment, there is a set of long vanes 170 that alternate with a setof splitter vanes 171. The portion of the long vanes 170 that is notpresent in the splitter vanes 171 is referred to as the “inducer” 173.Each vane 170, 171 has an inlet edge 172, a tip 174 that is proximate tothe outside edge 164, and a top surface 176 that is, in this example,flat in a generally circumferential direction about axis 161 while beingcurved in a generally radial direction. The region indicated by thedashed-line oval labeled “B” is shown in FIG. 6.

FIG. 6 is a close-up plan view of a vane tip 174 of the impeller 160 ofFIG. 5 according to certain aspects of the present disclosure. Theexample vane 170 has a leading surface 180 and a trailing surface 182that meet at the tip 174. The leading surface 180 comprises a firstportion 177 and a second portion 175. In this example, the secondportion 175 extends from the tip 174 with a radius R2 that is the sameradius as the outside edge 164. The first portion 177 abuts the secondportion 175 and continues with a radius R1 that is smaller than R2 andlarger than the radii conventionally used to round outside edges. Incertain embodiments, the radius R1 may be within the range of 0.03-0.20inch. In certain embodiments, the radius R1 may be within the range of0.12-0.18 inch. In certain embodiments, the radius R1 may be within therange of 0.14-0.16 inch. In certain embodiments, the radius R1 may beapproximately 0.15 inch.

Without being bound by theory, it is believed that the effect of theradius R1 may be to control the turbulence of the air at the tip 174 andreduce the velocity gradient in the air flow as the air leaves theimpeller 160, compared to a conventional vane that abruptly ends at theoutside edge with a sizable angle between the leading surface and theoutside edge, as is visible in the impeller 10 of FIG. 4. By smoothingthis transition over a larger area, e.g. the length of the first portion177 and possible the second portion 175, and redirecting the air flowdirection, the velocity gradient is reduced and the air flow may be lessturbulent as the air leaves the impeller 160 and passes through the slot126.

Each vane 170, 171 has a centerline 179 that is coincident with andbisects the top surface 176 between the leading and trailing surfaces180, 182. The vanes 170, 171 have a common width W taken perpendicularto the centerline 179, wherein W varies along the centerline 179. At acommon distance from the tip 174 along the centerline 179, the width Wof each vane 170, 171 will be the same, for at least the length of thesplitter vanes 171.

The shape and width of the vanes 170, 171 proximate to the secondportion 177 may be selected to simply enable the radius to be as largeas R1, compared to the constant-thickness vanes of a conventionalimpeller. In certain embodiments, the trailing surface 182 has a minimumradius that is greater than the radius of the first portion of theleading surface 180. In certain embodiments, the shape and location ofthe trailing surface 182 may be chosen to cooperate with the leadingsurface of the adjacent vane 170, 171 to control the pressure and/orvelocity of the air flowing between the leading and trailing surfaces180,182.

The height of the vanes 170, 171, i.e. the distance from the shapedsurface 166 to the top surface 176, varies from the inlet edge 172 andtip 174. In certain embodiments, the height is constant from the tip 174over the first and second portions 177, 175 of the leading surface 180.In certain embodiments, the shaped surface 166 has an outside portion163 that is proximate to the first and second portions 177, 175 of theleading surface 180. In certain embodiments, the shaped surface 166 isflat and perpendicular to the axis 16 in the outside portion 163.

FIG. 7 is a cross-section taken along section line A-A of the blower 100of FIG. 1 according to certain aspects of the present disclosure. Thearrows 101 and 102 respectively indicate how air is drawn in through theinlet 119 and directed by the impeller 160 into the collector 116. Themotor 120 is shown in schematic form and, in this embodiment, the rotor(not shown in FIG. 7) of the motor 120 is directly connected to theimpeller 160. The area indicated by the dashed-line box “C” is discussedin greater detail with respect to FIG. 8.

FIG. 8 is an enlarged view of the area C of FIG. 7 according to certainaspects of the present disclosure. The cross-section of impeller 160shows the top surface 166, a bottom surface 167, and the outside edge162. The upper edge 124U of the top housing portion 112T and the loweredge 124L of the bottom housing portion 112B are proximate to each otherand separated by a slot 126. In this embodiment, the edges 124U and 124Lboth have a radius R4 on an inside corner nearest to the impeller 160,with angled surfaces that extend outward at an included angle 174 towardthe collector 116. The radius R4 improves the efficiency of the nozzleformed by slot 126. The radius R4 of edges 124U and 124L induces the“Coand

effect,” wherein a flowing gas will tend to follow a curved surface morereadily than a sharp edge, in the gas flowing through the slot 126. Thisredirection of the gas flowing through the slot 126 produces a smoothertransition of flow and pressure with lower loss and reduced audiblenoise. In certain embodiments, R4 may be within the range of 0.01-0.30inch. In certain embodiments, R4 may be approximately 0.020 inch.

In this example, the reference line 170 is aligned with the peak of theradius R4 of lower edge 124L and the reference line 172 is aligned withthe peak of the radius R4 of upper edge 124U. Thus, the slot 126 isdefined by the reference lines 170, 172. In this example, the shapedsurface 166 at the outside edge 162 is aligned with reference line 170,i.e. the lower edge 124L of the slot 126, and the top surfaces 176 ofthe plurality of blades 170, 171 are each aligned with the referenceline 172, i.e. the upper edge 124U of the slot 126.

The gap between the top surface 176 and the upper inner surface 123 ofthe upper housing 112T is a path of potential backflow from the edge 162of the impeller 160 toward the center. Minimizing the gap 183 betweentop surface 176 and the upper inner surface 123 reduces this backflowand thereby improves the pressure recovery of the blower 100. In certainembodiments, the gap 183 may be in the range of 0.002-0.150 inch whenthe impeller 160 is stationary relative to the housing 112. In certainembodiments, the gap 183 may be in the range of 0.005-0.050 inch. Incertain embodiments, the gap 180 may be approximately 0.010 inch.

The lower edge 124L has an adjacent wall 120 with a gap 180 between theoutside edge 162 and the wall 120. In certain embodiments, the gap 180may be in the range of 0.0035-0.110 inch when the impeller 160 isstationary relative to the housing 112. In certain embodiments, the gap180 may be in the range of 0.005-0.050 inch. In certain embodiments, thegap 180 may be approximately 0.0073 inch. In certain embodiments, theradius R2 of the outside edge 162 of the impeller 160 may increase asthe rotational velocity of the impeller 160 increases and, therefore,the gap 180 may be reduced when the impeller 160 is rotating relative tothe housing 112. In certain embodiments, the impeller 160 may rotate ata rotational velocity of up to 60,000 rotations per minute (rpm)relative to the housing 112 and the gap may be reduced to as little as0.003 inch. As there will be a boundary layer (not visible in FIG. 8)attached to each of the wall 120 and the outside edge 162, reducing thisgap may decrease the portion of the gap wherein airflow may goturbulent, e.g. the portion between the two boundary layers, therebyreducing the acoustic energy generated by the turbulent air.

The wall 120 connects to a shelf 122. There is a gap 182 between thebottom surface 167 of the impeller 160 and the shelf 122 of the bottomhousing portion 112B. In certain embodiments, the gap 182 may be lessthan or equal to 0.020 inch when the impeller 160 is stationary ormoving relative to the housing 112B. In certain embodiments, the gap 182may be less than or equal to 0.050 inch. In certain embodiments, the gap182 may be less than or equal to 0.020 inch.

FIGS. 9A-9C are perspective views of the overmolded top housing 112Taccording to certain aspects of the present disclosure. FIG. 9A depictsa translucent view of a layer 200 of a sound-damping material formed soas to match the external profile of a housing shell 210 shown in FIG.9B. In this example, the sound-damping layer 200 covers most of theexternal surface of the housing shell 210 with the exception of theattachment points 212 for the clips 114 (not shown in FIGS. 9A-9C). FIG.9C shows combined top housing portion 112T with the sound-damping layer200 on the external surface of the housing shell 210.

In certain embodiments, the sound-damping layer 200 comprises anelastomer, e.g. a silicone or rubber, having poor acoustictransmissibility. In certain embodiments, the sound-damping layer 200may be overmolded on the housing shell 210. In certain embodiments, thesound-damping layer 200 may be applied to the housing shell 210 by oneor more of the processes of transfer molding, spraying, dipping,brushing, curtain coating, or other manual or automated coatingapplication process. In certain embodiments, the sound-damping layer 200may comprise high-density particles, e.g. steel, that may further reducethe transmissibility of the sound-damping layer 200.

It can be seen that the disclosed embodiments of the blower may provideadvantages in size, cost, performance, and reduced noise duringoperation. The shaping of the leading and trailing surfaces of the vanesnear the outside edge of the impeller may reduce the turbulence andvelocity gradient in the air flow around the tip of the vanes, therebyreducing the acoustic noise generated by the air flow. The smallclearances between portions of the impeller and portions of the housingmay further reduce the acoustic noise by decreasing the gaps compared tothe depth of the boundary layers, thereby reducing the portion of thegap susceptible to noisy, turbulent flow.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. While theforegoing has described what are considered to be the best mode and/orother examples, it is understood that various modifications to theseaspects will be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to other aspects. Thus,the claims are not intended to be limited to the aspects shown herein,but is to be accorded the full scope consistent with the languageclaims, wherein reference to an element in the singular is not intendedto mean “one and only one” unless specifically so stated, but rather“one or more.” Unless specifically stated otherwise, the terms “a set”and “some” refer to one or more. Pronouns in the masculine (e.g., his)include the feminine and neuter gender (e.g., her and its) and viceversa. Headings and subheadings, if any, are used for convenience onlyand do not limit the invention.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Some of the stepsmay be performed simultaneously. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

Terms such as “top,” “bottom,” “front,” “rear” and the like as used inthis disclosure should be understood as referring to an arbitrary frameof reference, rather than to the ordinary gravitational frame ofreference. Thus, a top surface, a bottom surface, a front surface, and arear surface may extend upwardly, downwardly, diagonally, orhorizontally in a gravitational frame of reference.

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as an “embodiment” does not imply that suchembodiment is essential to the subject technology or that suchembodiment applies to all configurations of the subject technology. Adisclosure relating to an embodiment may apply to all embodiments, orone or more embodiments. A phrase such an embodiment may refer to one ormore embodiments and vice versa.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.” Furthermore, to the extent that the term “include,” “have,” or thelike is used in the description or the claims, such term is intended tobe inclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A blower comprising: an impeller comprising: animpeller plate; and a plurality of blades each attached to the impellerplate and comprising a tip and a leading surface that comprises a firstportion proximate to the tip, the first portion having a first radius;and a housing comprising: an impeller cavity, wherein the impeller plateis disposed within the impeller cavity; a collector; and a slot betweenthe impeller cavity and the collector, the slot having an upper edge anda lower edge, wherein the upper and lower edges of the slot eachcomprises a respective inclined surface extending from the respectiveedge toward the collector and an inside rounded corner nearest theimpeller, the inclined surfaces disposed relative to each other suchthat a distance between the inclined surfaces increases as the inclinedsurfaces extend away from the impeller.
 2. The blower of claim 1,wherein the plurality of blades comprises a tip and leading surface thatcomprises a first portion proximate to the tip, the first portion havinga first radius, the first radius being within a range of 0.14-0.16 inch.3. The blower of claim 1, wherein: the impeller plate comprises anoutside edge with a second radius; the tip is coincident with theoutside edge of the impeller plate; the leading surface comprises asecond portion disposed between the tip and the first portion; and thesecond portion of the leading surface comprises the second radius. 4.The blower of claim 1, wherein the inclined surfaces are disposedrelative to each other at an angle within a range of 10-40 degrees. 5.The blower of claim 1, wherein: the impeller cavity further comprises anupper inner surface; each blade comprises a top surface; and a gapbetween the top surface at the tip of the respective blade and the upperinside surface of the impeller cavity is within a range of 0.005-0.050inch.
 6. The blower of claim 1, wherein: the housing comprises an insidewall that is proximate to the outside edge; and a gap between the insidewall and the outside edge is in a range of 0.035-0.110 inch when theimpeller is stationary.
 7. The blower of claim 1, wherein: the housingcomprises a shelf; the impeller plate further comprises a bottom surfaceproximate to the outer edge and disposed over a portion of the shelf;and the gap between the bottom surface of the impeller plate and theshelf of the housing is less than or equal to 0.050 inch.
 8. The blowerof claim 1, further comprising a sound-damping layer disposed on aportion of the housing.
 9. The blower of claim 8, wherein thesound-damping layer comprises a layer disposed on an external surface ofthe housing over the collector and impeller cavity.
 10. The blower ofclaim 8, wherein the sound-damping layer comprising an elastomer. 11.The blower of claim 1, wherein the collector is formed as a volute. 12.The blower of claim 1, wherein the impeller is formed as a centrifugalimpeller.
 13. The blower of claim 12, wherein: the top surface of eachof the plurality of blades comprises a centerline from the tip of therespective blade to an inlet end of the respective blade; each of theplurality of blades comprises a maximum width that is measuredperpendicular to the centerline and intersects the first portion of theleading edge.
 14. The blower of claim 13, wherein: each of the pluralityof blades comprises an initial width proximate to the inlet end of therespective blade; and the maximum width of each blade is at least twicethe initial width of the respective blade.
 15. A blower comprising: animpeller comprising: an impeller plate; and a plurality of blades eachattached to the impeller plate; and a housing comprising: an impellercavity, wherein the impeller plate is disposed within the impellercavity; a collector; and a slot between the impeller cavity and thecollector, the slot having an upper edge and a lower edge, wherein theupper and lower edges of the slot each comprises a respective inclinedsurface extending from the respective edge toward the collector and aninside rounded corner nearest the impeller having a radius within therange of 0.01-0.30 inches, the inclined surfaces disposed relative toeach other such that a distance between the inclined surfaces increasesas the inclined surfaces extend away from the impeller.
 16. The blowerof claim 15, wherein the inclined surfaces are disposed relative to eachother at an angle within a range of 10-40 degrees.
 17. The blower ofclaim 15, wherein: the housing comprises an inside wall that isproximate to the outside edge; and a gap between the inside wall and theoutside edge is in a range of 0.035-0.110 inch when the impeller isstationary.
 18. The blower of claim 15, wherein: the housing comprises ashelf; the impeller plate further comprises a bottom surface proximateto the outer edge and disposed over a portion of the shelf; and the gapbetween the bottom surface of the impeller plate and the shelf of thehousing is less than or equal to 0.050 inch.
 19. The blower of claim 15,further comprising a sound-damping layer disposed on a portion of thehousing.
 20. The blower of claim 19, wherein the sound-damping layercomprises a layer disposed on an external surface of the housing overthe collector and impeller cavity.